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According to an old stackoverflow thread [1], citing an even older comment by
Andy Polyakov (1875e6db29, Pull up Win64 support from 0.9.8., 2005-07-05),
a cast of 'SOCKET' (UINT_PTR) to 'int' does not create a problem, because although
the documentation [2] claims that the upper limit is INVALID_SOCKET-1 (2^64 - 2),
in practice the socket() implementation on Windows returns an index into the kernel
handle table, the size of which is limited to 2^24 [3].
Add this note to the manual page to avoid unnecessary roundtrips to StackOverflow.
[1] https://stackoverflow.com/questions/1953639/is-it-safe-to-cast-socket-to-int-under-win64
[2] https://docs.microsoft.com/en-us/windows/win32/winsock/socket-data-type-2
[3] https://docs.microsoft.com/en-us/windows/win32/sysinfo/kernel-objects
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16699)
75 lines
2.1 KiB
Plaintext
75 lines
2.1 KiB
Plaintext
=pod
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=head1 NAME
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SSL_set_fd, SSL_set_rfd, SSL_set_wfd - connect the SSL object with a file descriptor
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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int SSL_set_fd(SSL *ssl, int fd);
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int SSL_set_rfd(SSL *ssl, int fd);
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int SSL_set_wfd(SSL *ssl, int fd);
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=head1 DESCRIPTION
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SSL_set_fd() sets the file descriptor B<fd> as the input/output facility
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for the TLS/SSL (encrypted) side of B<ssl>. B<fd> will typically be the
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socket file descriptor of a network connection.
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When performing the operation, a B<socket BIO> is automatically created to
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interface between the B<ssl> and B<fd>. The BIO and hence the SSL engine
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inherit the behaviour of B<fd>. If B<fd> is nonblocking, the B<ssl> will
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also have nonblocking behaviour.
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If there was already a BIO connected to B<ssl>, BIO_free() will be called
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(for both the reading and writing side, if different).
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SSL_set_rfd() and SSL_set_wfd() perform the respective action, but only
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for the read channel or the write channel, which can be set independently.
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=head1 RETURN VALUES
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The following return values can occur:
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=over 4
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=item Z<>0
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The operation failed. Check the error stack to find out why.
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=item Z<>1
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The operation succeeded.
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=back
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=head1 NOTES
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On Windows, a socket handle is a 64-bit data type (UINT_PTR), which leads to a
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compiler warning (conversion from 'SOCKET' to 'int', possible loss of data) when
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passing the socket handle to SSL_set_*fd(). For the time being, this warning can
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safely be ignored, because although the Microsoft documentation claims that the
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upper limit is INVALID_SOCKET-1 (2^64 - 2), in practice the current socket()
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implementation returns an index into the kernel handle table, the size of which
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is limited to 2^24.
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=head1 SEE ALSO
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L<SSL_get_fd(3)>, L<SSL_set_bio(3)>,
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L<SSL_connect(3)>, L<SSL_accept(3)>,
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L<SSL_shutdown(3)>, L<ssl(7)> , L<bio(7)>
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=head1 COPYRIGHT
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Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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